This invention relates to well drilling apparatus, such as that used in drilling oil wells, and in particular to a new and improved apparatus for measuring the pressure on the drill bit.
In a typical well drilling rig, a drill bit is positioned at the lower end of a string of drill pipe, with the drill bit being driven by a motor actuated by mud pumped down the drill pipe. There is an optimum pressure which should be applied to the drill bit for maximum efficiency in drilling. Operating at a lower pressure means slower drilling, while operating at a higher pressure runs the risk of damage to the bit. Hence it is desirable that the operators on the surface of the ground at the drilling platform know the pressure on the drill bit so that drilling speed can be optimumly controlled.
In the past, pressure of the mud at the drill motor has been measured by lowering a sensor down the interior of the string of pipe. This does give a measure of pressure of the mud at the drill motor, and attempts have been made to relate this to pressure on the drill bit, but such have not been satisfactory. The problem is particularly difficult when angle drilling is being carried out, since the actual pressure on the bit is a combination of that due to mud pressure and that due to the weight of the string of drill pipe.
It is an object of the present invention to provide a new and improved apparatus for measuring the pressure on the drill bit in a well drilling apparatus. A further object is to provide such an apparatus which is especially suited for operation with angle drilling operations.
A further object is to provide such an apparatus which will measure the pressure adjacent the bit in the bottom of the hole and provide an indication of pressure at the surface for direct reading by the operator. An additional object is to provide such an apparatus which utilizes simple and reliable components which can be utilized in the area adjacent the drill bit.
These and other objects, advantages, features and results will more fully appear in the course of the following description.